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SUMMARY:Cajal bodies\, the nucleolus and fibrillarin are required for a pl
 ant virus systemic infection - Dr Michael Taliansky\, SCRI Dundee
DTSTART:20081023T150000Z
DTEND:20081023T160000Z
UID:TALK13478@talks.cam.ac.uk
CONTACT:3901
DESCRIPTION:The nucleolus and Cajal bodies are prominent interacting subnu
 clear domains involved in crucial aspects of cell function such as RNA met
 abolism\, the cell cycle and aging. Certain viruses interact with these co
 mpartments but the functions of such interactions are largely uncharacteri
 zed. We have recently shown that the ability of the Groundnut rosette viru
 s ORF3 protein to move viral RNA long-distances through the phloem\, the s
 pecialized vascular system used by plants for the transport of assimilates
  and macromolecules\, strictly depends on its interaction with Cajal bodie
 s\, the nucleolus and the major nucleolar protein\, fibrillarin. The ORF3 
 protein targets and re-organizes Cajal bodies into multiple Cajal body-lik
 e structures and then enters the nucleolus by causing fusion of these stru
 ctures with the nucleolus. This process is mediated by the interaction bet
 ween ORF3 protein and fibrillarin leading to the formation of ring-like co
 mplexes. Using atomic force microscopy we have determined the architecture
  of these complexes as single-layered ring-like structures with a diameter
  of 18-22 nm and height of 1.9-2.5 nm which consist of equal number (6-8) 
 of ORF3 protein and fibrillarin molecules. A model of structural organizat
 ion of fibrillarin-ORF3 protein complexes will be presented. It is suggest
 ed that ORF3 protein and fibrillarin can move from the nucleus to the cyto
 plasm in a form of these ring-like complexes. Furthermore\, in the cytopla
 sm\, these rings formed by both ORF3 and fibrillarin proteins interact wit
 h viral RNA encapsidating it and re-organizing it into helical structures\
 , and thereby play a key role in the assembly of umbraviral RNP complexes 
 capable of long-distance movement and systemic infection. These results de
 monstrate novel functions for fibrillarin as an essential component of tra
 nslocatable viral RNPs and may have functional implications for other plan
 t viruses and development of new approaches to control virus defence respo
 nses which will be discussed.\n\nhttp://www.scri.ac.uk/staff/MichaelTalian
 sky
LOCATION:Department of Plant Sciences\, Large Lecture Theatre
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